Elastic fluid turbine



June 14, 1932. c. A. PARSONS ET AL ELASTIC FLUID TURBINE Filed NOV. 12, 1930 'INVENTORS g wszw 1am BY THElR ATTORNEYS d w ya A9 Patented June 14, 1932 UNITED STATES PATENT OFFICE CHARLES ALGERNON PARSONS, ALFRED QUINTIN CARNEGIE AND FRANCIS WILLIAM GARDNER, OF NEWCASTLE-ON-TYNE, ENGLAND; SAID CARNEGIE AND SAID GARD- NEE ASSIGNORS TO SAID PARSONS; KATHARINE PARSONS, VINCENT THOMPSON AND FREDERICK GORDON HAY BEDFORD, LEGAL REPRESENTATIVES OF SAID CHARLES ALG-ERNON PARSONS, DECEASED ELASTIC FLUID TURBINE Application filed November 12, 1930, Serial No. 495,032, and in Great Britain February 11, 1930.

The invention relates to elastic-fluid turbines and particularly to the blades thereof. Experience shows that in reaction steam turbines, the rotor blades are eroded or corroded particularly in the region of thertips at the low pressure end of the turbine, and

it is believed that this erosion is due to impact of the blades with particles of water.

In view of the fact that at the low-pressure end of the turbine, the axial velocity of such particles is very small, the direction in which the moving blades strike them is substantially circumferential, so that all but a small zone of any particular blade is pro- 5' tected by the preceding blade.

Further, erosion is found to be most marked in those cases where the exposed part of the blade meets the water particles in a direction substantially normal to its surface.

The main object of the present invention is to provide improved or alternative means for reducing or minimizing the erosion in question and with such an object the in- .zb vention consists in reaction turbine blades of the well known Parsons type having the characteristics hereinafter set forth in the claims appendant hereto.

With such an object The present invention consists in a turbine in which the part of each blade or some of the blades that suffer erosion is provided with one or more flat or substantially flat surfaces inclined to the line of impact.

The invention also consists in the improved t-urboblading and turbines or turbine rotors titted therewith to be hereinafter described or indicated.

Referring to the accompanying diagrammatic drawing Figure 1 shows a side elevation and Figure 2 a cross-section on the line 22 of Figure 1 through two adjacent blades according to one form of the invention;

Figures 3 and i show an elevation and plan respectively of blades according to the present invention in which the inlet edge is cut back to leave a flat extending over part of the length of the blade,

Figures 5 and 6 showing views similar to Figures 4 and 5 in which the part cut away is of tapered form; while finally Figure 7 shows a side elevation and Figure 8 a cross-section on the line 8-8 of Figure 7 of a blade according to a modified form in which the flat surface is formed on a shield attached to the blade, 1.

The direction of motion of the blades is indicated by an arrow in Figures 2, if, 6 and 8.

In carrying the invention into effect according to the form shown in Figures 1 and 2, as applied, by way of example, to the lowpressure rotor blades of a steam reaction turbine, the blades, a, a, are so formed that, over the part liable to erosion, the curved face on the forward side of the leading or thick edge, that would receive the impact of the water particles in a direction substantially normal to its surface, is machined or otherwise treated so that it is replaced by a fiat, Z), or substantially flat surface lying at an angle to the relative direction of impact of the blade and water particles.

The flat surface thus formed lies across the end of the blade in the position indicated and is parallel to the length or axis of the blade.

As, in general, only that part of each blade towards the tip suffers from erosion, the flat, Z), extends for only a part of the length of the blade as shown in Figure 1. i

The fiat may intersect the working surface, c of the blade so as to form. an actual bevel as shown in Figure 2, or it may lie between curved portions of the back of the blade.

By thus making the impingement oblique instead of substantially normal, the erosive effect of the impact of the blade and water particles is reduced or entirely avoided.

It will be seen from Figure 2, that the direction of impact of the blades and particles, shown by the dotted lines, is nearly circumferential, the axial velocity of the water particles being small in relation to the tip speeds of the blades; only a comparatively small area of each blade is thus left unshielded by its neighbour.

According to a modified form of the invention, (see Figures 3 and it) the inlet edge of the blade is cut back for a substantial distance to form a fiat, b, extending a certain distance from the tip to correspond with the region where erosion is greatest. The fiat, I), over its working length runs parallel to the length of the blade, as shown in Figure 3, and is then formed with a fillet, 5 extending to the inlet edge.

A binding wire", 0, is shown passing through holes in the blades to maintain them in their correct relative position.

In Figures 5 and 6, the part of the inlet edge cut away to leave the flat, 6, instead of running parallel to the length of the blade is of maximum width at the tip and decreases to zero at any desired point further along the blade and such flat of decreasing width may end in any suitable form.

In the particular blade illustrated, two binding strips, 0 0 are shown notched into the body of the blade.

Instead of the usual blade formed of a homogeneous metal, the invention can also be applied to blades in which some form of shielding or sheathing is provided and in particular to blades having localized shields of the kind described in the specification of British Patent No. 309235, granted to the present applicants, and in this case, the localized shields themselves are provided with the inclined surfaces.

Thus, referring to Figures 7 and 8, the blade proper is shown at a, and the localized shield at c, the flat, b, in this case being I formed as a bevel on the shield.

In any form of the invention, more than one angled surface or fiat may be provided, the individual surfaces, if desired, being inclined to the direction of impact at somewhat difl'erent angles, while a slightly curved surface, either" convex or concave, may be provided in other cases to control the direction in which the water particles are thrown off, without materially affecting the result as regards' the reduction of erosion.

Moreover, apart from the form of the invention shown in Figures 5 and 6, the angled surfaces or flats of any other form of the invention may run in a direction inclined to the length of the blade, that is to say, an angled surface may be so disposed that the water particles are thrown from it in a direction having a radial component.

Other variations may be made in the particular examples described without exceeding the scope of the invention.

We wish it to be understood that in the claims appendant hereto, the word blade isused as including the case of a compound blade having a body and a protective sheath or like attachment thereto.

Havingnow described our invention, what we claim as new and desire to secure by Letters Patent is I. A reaction turbine blade of the Parsons type in which a certain region of the blade tip liable to impact with water particles and disposed on the convex side of the inlet edge is modified by the provision thereon of an elongated erosion-resisting flat inclined to the direction of said impact, the length of said flat being longitudinal of said blade.

2. A reaction turbine blade of the Parsons type as claimed in claim 1, in which the plane of said erosion-resisting flat is parallel to the length of said blade.

3. A reaction turbine blade of the Parsons type as claimed in claim 1, in which said erosion-resisting fiat crosses from the convex to the concave side of said blade and takes the form of abevel.

4. A reaction turbine blade of the Parsons type as claimed in claim 1, in which said erosion-resisting flat crosses from the convex to the concave side of said blade and is set back from the leading edge.

5. A reaction turbine blade of the Parsons type as claimed in claim 1, in which said erosion-resisting flat is set back from the inlet edge at the extreme tip thereof and decreases in width progressively along part of the length of the blade.

6. A reaction turbine blade of the Parsons type as claimed in claim 1, in which said blade at the tip is of compound construction including a localized shield, said erosion-resisting flat being formed on said shield.

In testimony whereof we have signed our names to this specification.

CHARLES ALGERNON PARSONS.

ALFRED QUINTIN CARNEGIE.

FRANCIS WILLIAM GARDNER. 

